Chromium for wear resistance



Dec. 17, 1946.

H. VAN DER HORST CHROMIUM FOR WEAR RESISTANCE Filed Feb. 22, 1943 2Sheets-Sheet l INVENTOR HfA/DP/lf mm an? #0257 BY 3 ATTORN EY 1946. H.VAN DER HORST 2,412,698

GHROMIUM FOR WEAR RESISTANCE .Filed Feb. 22, 1945 2 Sheets-Sheet 2 5% 4INVENTOR ATTORNEY Patented Dec. 17, 1 946 2,412,698 CHROMIUM roe WEARRESISTANCE v Hendrik van der Horst, Olean, N.

Y., assignor to Van der Horst Corporation of America, Olean,

a corporation of Delaware Application February 22, 1943, Serial No.476,753 In Great Britain September 3, 1938 (01. sea- 2) 27 Claims.

This invention relates to chromium wearing surfaces, i. e. surfacessubject to friction, and especially cylinder bores.

It is known that by providing a surface layer of chromium on thecylinder bores of engines, pumps, air compressors and the like the rateof wear of the bore can be very greatly reduced as the chromium layer isextremely hard and is also highy resistant to corrosion.

The chromium layer can be deposited electrolytically on the cylinderbore, and owing to the -hardness of the chromium it is desirable thatthe deposited chromium should be of such a form and thickness that aminimum of mechanical finishin of the surface is required. It is alsodesirable that'the finished surface of the chromium should not be toosmooth as a highly polished chromium surface is liable to pick up underworking conditions, that is, to be torn away from the surface of thecylinder bore.

Accordin to my invention a cylinder bore is provided with a layer orcoating of chromium in the surface of which are formed numerous smallgrooves, pits or depressions. Under working conditions oil is retainedin these and there is no tendency for the chromium to pick up. Further,

such a finely irregular chromium surface permits the piston rings togrind the chromium layer sufliciently to form a close fit between therings and cylinder early in their life, despite the extreme hardness ofchromium as a metal, and also permits the face of a chromium layer to beworked reasonably readily, for example for finishing closely to size.

In a preferred method of forming these grooves, pits or depressions alayer of chromium of the v desired thickness or f slightly more than therequired thickness is deposited electrolytically on the cylinder bore bythe process described in Patent No. 2,048,578 employing an aqueouschromic acid bath or solution as described therein and an anode ofcircular cross-section and of a diameter only slightly less than that ofthe cyldescribed in that patent.

area of the grooves, pits or depressions relative to the total area ofthe surface depend to a certain extent on the length of the treatmentwith reversed current and the current density employed, and after aprolonged treatment the surface may have the appearance of an' opengrain cast iron.

The treatment of the chromium with reversed current, i. e. with currentflowing in such a direction that the chromium serves as an anode, may becarried out in the same bath as the deposition of the chromium butpreferably it is carried out in a separate bath to avoid. spoiling thesolution. The solution in the second bath is preferably a chromic acidsolution as used in the first bath, but various otheracid or alkalinesolutions such as a 20% caustic soda solution may be employed.

Experiments have shown that a suitable surface can be obtained bytreating a smooth chromium deposit with a reversed current of from to450 ampere-minutes per square decimeter.

In addition to their function of retaining oil the grooves, pits ordepressions in the surface 'of the chromium reduce the efiective area ofthe surface which is in contact with a piston or other member working inthe cylinder bore and so reduce friction. Further, the reduction in theeffective-surface area facilitates any honing or grinding of the surfacewhich may be subsequently carried out to bring it exactly to size asthere is less chromium to remove.

As a certain amount of chromium is removed when the surface is treatedwith a reversed current it is desirable in depositing the chromiuminitially on a cylinder bore to deposit a layer of chromium of suchthickness that the internal diameter of the bore is approximately onethousandth of an inch under the required finished diameter.

To avoid excessive removal of chromium from the deposited layer at theends of the cylinder bore when the current is reversed, cylindricalextensions having the same diameter as the cylinder bore may betemporarily secured to the ends of the cylinder block or liner inalignment with the bore.

If desired the surface of the chromium layer after deposition may belightly honed to remove any projections or high spots before thechromium is treated with the reversed current.

A chromium surface in accordance with my invention is particularlyadapted for use in the cylinders of engines having aluminum pistons andcan be applied to cylinder blocks, barrels or liners of castdron, steelor any other metal on which chromium can be deposited electrolytically,and it can also be applied to other cylindrical bores.

The subject matter claimed herein was claimed initiallyin my copendingapplication Serial No. 270,018. filed April 25, 1939, on which PatentNo. 2,314,604 was issued March 23, 1943, and of a part of which thispresent application is a continuation. All claims to that subject matterwere removed from that application on the ground that such subjectmatter is separate and distinct from the method or process of the claimsretained in that application.

While the invention is described above as particularly applicable tocylinders for engines, pumps, compressors and the like, it can beapplied to chromium or otherwise chromium-faced wearing members of otherkinds, that is to say members tending to Wear by frictional contact withco-operating members, where the retention of lubricating oil between thecontacting members is desirable, or where the chromium is liable to bepicked up, or which require honing to size, etc.

Briefly, as appears above, my preferred method of producing, forexample, an engine cylinder or cylinder liner of my invention, thechromium being on the interior cylindrical wall of the cylinder orliner, is to take a cylinder block or liner of cast iron or ofothermetal suitable for the foundation and having a bore that is somewhatoversize, and plate the bore with chlromium electrolytically until thediameter of the bore is less than the diameter desired when finished;then apply the reverse current treatment, that is to say, subject thechromium plate to the electric current in such a direction that theexposed face of the chromium is an anode while in an electrolytic bathcapable of removing chromium from the surface with the passage of thecurrent, until the exposed surface or face of the'chromium is wellpitted or porous; and then hone the so treated surface of the chromiumto the size desired, and at least usually to a depth short of thebottoms of the grooves or pores resulting from the current, and usuallyusing first a rough hone and then a finer one to finish. Wearing membersother than cylinders can be produced by the same process in a mannerthat will be understood from the above. It will be understood of coursethat the chromium need not be pitted or perforated completely through,c. g., to any underlying metal forming a foundation for the chromium;preferably at least the grooves, pits or depressions extend only partway through the chfifnium. Within the term honing and the like as hereused, I include abrasive actions. In some instances or for some purposesit may not be necessary to hone the porous surface as initiallyproduced, e. g., as produced by the anodic current action, or it may beproduced as a chromium faced article that is readily treated further, orit may be sufficient to abrade or smooth the initial porous surface onlyslightly so as to,

for example, merely remove minor projecting or highspots.

The accompanying drawings illustrate the type of article that-resultsfrom this process which I prefer, and are representative generally ofthe article of my invention. Fig. 1 is a highly magnified view of atypical face or exposed surface of the chromium on which no honing hasbeen done, looking directly at the face. Fig. 2 is a magnified view of across-section of an article having such a surface or face. Figs. 3 and 4are magnified views of a typical surface or face, and a cross-section,after a material amount of honing. In tne drawings forming part of thepatent application, the magnification of Fig. 1 is about 500 diametersand the magnifications of Figs. 2, 3, and4 are about 100 diameters.

In Figs. 2 and 4, the numeral l indicates a foundation metal carrying anelectroplate 2 or 3 of chromium. In Figs. 1 and 3 only the chromium isshown of course.

Speaking generally, the chromium face of an article of my inventioncontains a great many cannot be distinguished one from another in a faceview. The bottoms of some or all of these depressions 4 and 5 may beirregular, the irregularities being of microscopic dimensions butsufficiently large to be measureable under a magnification of diameters,Figs. 2 and 4; for example, these major depressions 4 and 5 may havesmaller depressions in their bottoms, Figs. 3 and 4, and in someinstances and especially those 5 after honing, may have projectionsextending upwardly from their bottoms and forming smaller cavities. Atleast some of these major depressions 4 and 5 (whether individuallydistinguishable in a face view or not) are more than about 0.00015 inchand less than about 0.004 inch in width, and few if any are more thanabout 0.0125 inch in width. Preferably at least some of them are lessthan 0.004 inch in width and the widest are between about 0.0002 inchand about 0.0125 inch in width. Preferably in any instance the narrowestof the major number of the major depressions such as 4 and 5 that areobservable under a magnification of 500 diameters, is between about0.00003 inch and about 0.004 inch in width, and the widest of such majornumber is between about 0.0003 inch and about 0.0125 inch in width. Withthe depressions or major depressions 4 and 5 of such widths the grooves,pits or depressions in the chromium face or surface are of capillarysize and hence tend strongly to retain lubricating oil supplied to them.The depressions 4 and 5 may occupy anything more than six percent of thetotal area of theworking face, thus exposing adequate oil at the face.Preferably the major number of the depressions are more than 0.0002 inchdeep.

Prior to any honing that may be done or when the face has been onlyrelatively slightly abraded, and provided that the facially-apparentdepressions 4 are not too numerous, a microscopic view of sufficientmagnification looking perpendicularly at the face of the chromium, Fig.1, shows these depression: 4 as narrow cracks or crevices distributedover the face, each extending as a more or less straight or slightlycurved line, with few if, any exceptions of lengths many times greaterthan their average widths, the crevices or cracks extendin in manydifferent directions and crossing each other to form a network ornetworks of crevices, and which are s numerous that the areas standingbetween the crevices are of microscopic dimensions. However the cracksor crevices such as 4 may be so numerous that individually they areindistinguishable one from another in a face view such as Fig. 1. Insuch a case a microscopic view looking directly at an unhoned or aslightly abraded face is of the nature to be expected of such astructure, for example a conglomerate of metal at different levels, orexceedingly small areas of metal in focus and irregularly distributedthroughout a depressed area in the midst of which other metallic areas,points or ridges may appear as blurs. Accordin to my invention thecracks or crevices 4 (regardless of whether or not they are so few innumber as to be individually distinguishable in a face view as inFig. 1) include some that are more than about 0.00015 inch and less thanabout 0.00125 inch in width. Preferably the Widest of them is betweenabout 0.0003 inch and 0.0009 inch in width, and more preferably thewidest of them is between 0.0004 inch and about 0.0009 inch in width.Most preferably in any instance the major number of the cracks orcrevices 4 that are observable at a magnification of 500 diameters, areof various widths, the narrowest of that major number is between about0.00003 inch and about 0.00009 inch in width and the widest is betweenabout 0.0004 inch and about 0.0009 inch in width. The number of thecracks or crevices 4 (as counted by the number of those observable at amagnification of 500 diameters that, per inch, cross a straight line,the average of a number of such counts being taken in any case), may beanywhere from about 400 per inch to such a number (usually above 1000per inch) that the crevices merge into each other to such an extent asto be indistinguishable one from another; preferably I provide more thanabout 500 per inch. The cracks or crevices 4 may occupy anywhere fromsix per cent to substantially one hundred percent of the total area' ofthe face,

depending on th porosity desired. In any instance the crevices may be ofvarious depths, and the depths of at least the major number of them (asmeasurable ina magnified cross-section such as Fig. 2) may be anythinggreater than about 0.00018 inch; preferably I make the depths of thedeepest of them between about 0.0017 inch and about .0035 inch; morepreferably Imake the depths of at least the major number of those thatare observable at a magnification of 500 diameters, between about 0.0002inch and about 0.0035 inch. The number of the cracks or crevices 4produced by passing current through the chromium with the chromium asthe anode as above described. the widths of the widest of those cracksor crevices at the end of such operation,

and the percent of the total area of the face treated occupied by thecracks or crevices, de-- pend on the number of ampere-minutes per unit'of area employed in that operation, generally speaking, e. g, as a rule300 ampere-minutes per.

square decimeter produces both more crevice and crevices of greaterwidths, and causes the crevices to occupy a greater part of the totalarea of the face, than 150 ampere-minutes per square decimeter, and soon until the number and widths of the cracks or crevices become so greatrelative to each other that they occupy the whole face and the cracks orcrevices are no more distinguishable one from another. However, at timesat least the depths of the deepest crevices directly resulting from suchcurrent operations, as seen in cross-sectional views, does not seem tovary so directly with the amount of energy used in the operation; in anycase however the needed depths are readily achieved.

After a more or less thorough honing the structure described aboveassumes the form illustrated in Figs. 3 and 4. As shown representativelyin Fig. 3, a microscopic view looking perpendicularly at the face orexposed surface of the chromium shows this face to consist of,primarily, a plane area or areas 5 of metal and the more or lessuniformly distributed major depressions 5 mentioned before and whichextend below the level of the plane area or areas 6. Additionally, muchsmaller or minor pits or depressions may be 'distributed more or lessthroughout the metal area or areas 6 as may be seen in the upperright-hand quarter of Fig. 3 where the focus is sharper. I use the term"plane area here in the sense of tooled, or finished, or relativelysmooth, rather than in the sense of wholly flat, since in fact they maybe curved, e. g.. when the chromium forms the face of the internalcylindrical wall of an engine cylinder. The minor pits or smalldepressions referred to above appear to be composed in whole or in partof remnants of some of the smaller or minor grooves, pits ordepressionsof the form of the article of Figs. 1 and 2; at times theyappear to be collected along lines such as those of the cracks orcrevices 4 although at other times such disposition may be hard toobserve. For the most part at least. these minor pits or depressionswithin the plane area or \areas 6 may be so minute in length and widthat the level of 6 that it is substantially impossible to measure thesedimensions with any material degree of certainty even at a magnificationof 500 diameters. Desirably the major depressions 5 are generallyelongated (although'the differences between their respective lengths andwidths may be greatly less than the differences between the lengths andwidths of the respective cracks or crevices 4), and desirably are ofhigher irregular shapes as seen in a face view such as Fig. 3. Generallyspeaking, and other things being the same, the greater the degree ofporosity given to the chromium face prior to honing, the greater is thepercentage of the total surface that is occupied by major depressionssuch, as 5. the greater their lengths, and the greater their lengthsrelative to their average widths, and the more they tend to be connectedone with another and to divide the plane metal areas 6 into the form ofisolated islands. The greater the honing in any instance the greater isthe percentage of the total face area occupied by the plane metal areas6 and, generally speaking, the shallower are the grooves, pits ordepressions, and accordingly the smaller is the percentage of the totalface area occupied by major depressions such as 5, and the less theporosity of the face of the chromium.

The maximum width of at least some of the depressed areas 5 may be morethan about 0.00015 inch and less than about 0.004 inch. Preferably atleast some of them are less than about 0.004 inch in maximum width andthe widest are between about 0.002 inch and about 0.0125 inch in maximumwidth; and preferably the narrowest of them are between about 0.0001inch and about 0.004 inch in width. Preferab y the depressed areas 5occupy between six per cent and seventyfive per cent of the totaloperating area of the face, dependent on the conditions such as the loadto be borne and the degree of porosity desired for oil retention.Usually I make the facially-apparent depressions 5 between about 0.00006inch (preferably about 0.00015 inch) and about 0.003 inch in depth; theymay be of various depths.

It will be understood of course that my invention is not limited to thematter as specifically described above nor to the particular structuresillustrated in the drawings except as appears in the claims hereafter.

I claim:

1. A wearing member having a wearing surface consisting of chromium anda body formed of another material, and in which wearing surface aregrooves, pits or other depressions which, in number, size and depth, areat least of the order of the grooves, pits or other'depressions whichresult from treating an electroplated chromium surface to a reversedcurrent for from 150 to 450 ampere-minutes and then honing to finish.

2. A member having a surface to operate in wearing contact with anothermember, said surface consisting substantially of chromium in which thereare small grooves, pits or depressions at least equal in number, size,depth and distribution, to the number, size, depth and distribution ofthe grooves, pits or depressions which result from passing a currentthrough a chromium plated surface, in an electrolyte, and in such adirection that the chromium is an anode, until about 150 ampere-minutesof electricity per square decimeter of the surface has passed throughthe surface and thereafter honing the surface to finish.

3. A member having a wearing surface consisting substantially ofchromium and a body formed .of another material, and in which wearingsurface there are small groovesfpits or depressions of at least thenumber, size, depth and distribution of the grooves, pits or depressionswhich result from passing a current through a chromium plated surface,in an electrolyte, and in such a direction that the chromium is ananode, until about 150 ampere-minutes of electricity per squaredecimeter of the surface has passed through the surface and thereafterhoning the surface to finish.

4. A member having a surface to engage in moving contact with anothermember, said surface of the first mentioned member consisting ofchromium and the body of said first men-v tioned memberbeing formed ofanother material, and there being in the exposed surface of the chromiumgrooves, pits or other depressions to contain lubricant, thedistribution, number, size and depth of said grooves, pits ordepressions being at least as great approximately as the distribution,number, size and depth' of those grooves, pits or depressions whichresult from passing a current through an electroplated chromium surface,in an electrolyte, and in such a. direction that the chromium is ananode, until from about 150 to about 450 ampere-minutes of electricityper square decimeter of the surface has passed through the surface andthereafter honing the surface to finish.

5. A cylinder of which the bore is coated with a layer of chromium inthe surface of which are numerous small grooves, pits or depressionsadapted to retain oil, the number, size, depth and distribution of saidgrooves, pits and depressions being at least equal to substantially thenumber, size, depth and distribution of the grooves, pits or depressionsproduced by treating a chromium plated surface, in an electrolyte, to acurrent, with the chromium as an anode, until about 150 ampere-minutesof electricity per square surface and honing to finish.

6. A wearing member having a face of chromium to operate in frictionalcontact with another wearing member, there being a multitude of smalldepressions in said face and the bottoms of at least many of saiddepressions being irregular, the irregularities of such bottoms being ofmicroscopic dimensions but of sufficient size to be measurable under amagnification of 100 diameters.

7. A wearing member having a face of chromium to operate in frictionalcontact with another wearing member, there being a multitude of smalldepressions in said face and at least many of said depressions havingsmaller depressions on their bottoms.

8. A wearing member having a face of chromium to operate in frictionalcontact with another wearing member, there being in said face amultitude of depressions at least some of which, as observable lookingdirectly at the face, are more than about 0.00015 inch and less thanabout 0.004 inch in width.

9. A wearing member having a face of chromium to operate in frictionalcontact with another wearing member, there being in said face amultitude of depressions at least some of which, as observable lookingdirectly at the face, are more than about 0.00015 inch and less thanabout 0.004 inch in width and few if any are more than about 0.0125 inchin width.

10. A wearing member having a face of chromium to operate in frictionalcontact with another wearing member, there being in said face amultitude of depressions of various widths, and, as observable lookingdirectly at the face, at least some of said depressions being less thanabout 0.004 inch in width and the widest being between about 0.0002 inchand about 0.0125 inch in width.

11. A wearing member having a face of chromium to operate in frictionalcontact with another wearing member, there being in said face amultitude of depressions of various widths and of which the narrowest ofthe major number observable looking directly at the face at a mag,-nification of 500 diameters is between about 0.00003 inch'and 0.004 inchin Width and the widest of said major number is between about 0.0003inch and about 0.0125 inch in width.

'12. The subject matter of claim 11 characterized by the fact that thesaid depressions in the face occupy more than six percent of the totalarea of the face.

13. The subject matter of claim 11 characterized by the fact that themajor number of said depressions are more than 0.0002 inch deep.

14. An article of manufacture having a face of chromium in which thereare crevices extending in many directions and which are so numerous thatany areas standing between the crevices are of microscopic dimensions.

15. An article of manufacture having a face of chromium in which thereare individually distinguishable crevices extending in many directionsand crossing each other to form a network and which are so numerous thatthe areas standing between the crevices are of microscopic dimensions.

16. An article of manufacture. having a face of chromium in which thereare crevices extending in many directions, and at least many of the saidcrevices being so narrow that, in face view, they are individuallyindistinguishable.

17. A wearing member having a face of chr0- mium to operate infrictional contact with another wearing member, there being n said facea multitude of depressions having the form of crevices at least some ofwhich are more than about 0.00015 inch and less than about 0.00125 inchin width. v

18. A wearing member having a face of chromium to operate in frictionalcontact with an- 9 other wearing member, there being in said face amultitude of depressions having the form of crevices the maximum width.of the widest of which is between about 0.0004 inch and about 0.001inch in width.

19. A wearing member having a face of chromium to operate in frictionalcontact with another wearing member, there being in said face amultitude of depressions having the form of crevices of various widths,andof which the narrowest of the major number observable at amagniilcation of 500 diameters is between about widest is between about0.0004 and about 0.0009 inch in width.

20. The subject matter of claim 19 characterized bythe fact that saidcrevices occupy between six percent and about one hundred percent of thetotal area of the face. i

21. The subject matter of claim 19 characterized by the fact that themajor number of said crevices are between about 0.0002 inch and about.0035 inch deep.

22. A wearing member having a face of chromium to operate in frictionalcontact withanother wearing member, said face being composed primarilyof interspersed plane and major depressed areas, at least many of saidmajor depressed areas having projections rising from their bottoms andforming small cavities.

23. A wearing member having a face of chr0- mium to operate infrictional contact with another wearing member, said face being composedprimarily of interspersed plane and mailor depressed areas. at leastsome of the major depressed areas being more than about 0.00015 inch andless than about 0.004 inch in maximum width.

24. A wearing member having a face of chromium to operate in frictionalcontact with another wearing member, said face being composed primarilyof interspersed plane and major depressed areas, at least some of themajor depressed areas being less than about 0.004 inch in maximum widthand the widest being between about 0.002 inch and about 0.0125 inch inmaximum width.

25. A wearing member having a face of chromium to operate in frictionalcontact with another wearing member, said face being composed primarilyof interspersed plane and major depressed areas, the major depressedareas being of various widths, the narrowest of them being between about0.0001 inch and. about 0.004 inch in maximum width, and the widest ofthem being between about 0.002 inch and about 0.0125 inch in maximumwidth.

26. The subject matter of claim 22 characterized by the fact that thesaid major depressed areas occupy between six percent and seventyfivepercent of the total area of the face.

27. The subject matter of claim 22 characterized by the fact that atleast the larger number of said major depressions are between about0.0001 inch and about 0.003 inch deep.

1 HENDRIX van on HORST;

